University Physics Al No. 7Impulse, Momentum, and Collisions Class Number ame I. Choose the Correct Answer An object is moving in a circle at constant speed v. The magnitude of the rate (A)is zero(B)is proportional to v. (C)is proportional to v2.(D)is proportional to y c) momentum of the object Solution The magnitude of the centripetal acceleration is constant for uniform circular motion, that constant Using the general statement of Newton s law of motion Fotal m F,=ma =m-ov 2. If the net force acting on a body is constant, what can we conclude about its momentum? A)The magnitude and/or the direction of p may change (B)The magnitude of p remains fixed, but its direction may change (C)The direction of p remains fixed, but its magnitude may change D) p remains fixed in both magnitude and direction Solution Using the general statement of Newton's law of motion Fta= -total, we can know the magnitude and/or the direction of p may change 3. If I is the impulse of a particular force, what is d/ /dt? (C) A)The momentum(B) The change in momentum(C)The force(D) The change in the force Solution According the definition of the impulse, di=Fdt==FUniversity Physics AI No. 7 Impulse, Momentum, and Collisions Class Number Name I．Choose the Correct Answer 1. An object is moving in a circle at constant speed v. The magnitude of the rate of change of momentum of the object （ C ） (A) is zero (B) is proportional to v. (C) is proportional to v 2 . (D) is proportional to v 3 . Solution: The magnitude of the centripetal acceleration is constant for uniform circular motion, that is constant 2 = = r v ac , Using the general statement of Newton’s law of motion t p F total total d d v v = , we have 2 2 d d v r v F ma m t p total c total = = = ∝ v v 2. If the net force acting on a body is constant, what can we conclude about its momentum? (A) The magnitude and/or the direction of p r may change. （ A ） (B) The magnitude of p r remains fixed, but its direction may change. (C) The direction of p r remains fixed, but its magnitude may change. (D) p r remains fixed in both magnitude and direction. Solution: Using the general statement of Newton’s law of motion t p F total total d d v v = , we can know the magnitude and/or the direction of p r may change. 3. If I r is the impulse of a particular force, what is dI / dt r ? （ C ） (A) The momentum (B) The change in momentum (C) The force (D) The change in the force Solution: According the definition of the impulse, F t I I F t r r r r = ⇒ = d d d d